Mixed IOM12 and IOM6 shelves in stack possible?

Hi,

I just bought some DS224 shelfs (IOM12) and wanted to add them to our FAS2750 stack with DS2246 shelfs (IOM6). This resulted in the message "Cabling together disk shelves 1.4 of IOM12 and 1.3 of IOM6 is not supported." As far as I remember in the past it was possible to mix a stack with IOM3 and IOM6 shelfs. Is there maybe a newer version of ONTAP supporting the mixed IOM6/12 stack? We are running verion 9.6P2 now.

thanks for your help!

Regards, Maurice